Effects of sampling and propagation loss on ultrawideband synthetic aperture radar

military advantages are obvious. However conventional SAR implementations haveproven to be ineffective.The technical issue facing a FOPEN radar is the balance between resolution and the propagation loss due to foliage.Range resolution is given approximately by c/2B where c is the speed of light and B is the radar signal bandwidth. Thus arange resolution of 0.3 meters requires a bandwidth of 0.5 GHz. Conventional radar technology produces signal bandwidthsequal to 5-10% of the carrier frequency. Thus a 0.5 GHz bandwidth requires a 5-10 0Hz carrier frequency. Unfortunatelypropagation loss due to foliage is severe in this frequency range (see section 7) so that only very short foliage penetrationdepths can be obtained. Lowering the center frequency to reduce attenuation also degrades range resolution if the percentagebandwidth is fixed.An impulse type UWB signal has a relatively wide bandwidth combined with a low center frequency. For instance,a bipolar UWB pulse of duration, T, has a center frequency, f0, given approximately by f0=lfT and a two-sided bandwidth, B,also approximately given by B=1/T. Thus a 2 nanosecond duration pulse would have a 0.5 GHz bandwidth centered about